Protein exchange and self recognition in myxobacteria biofilms

描述（由申请人提供）：生物膜是附着在感染部位表面的微生物群落，具有重要的医学意义，因为它们可以抵抗抗生素和免疫系统的杀伤。了解生物膜细胞如何相互作用以引起表型变化的进展受到探测其细胞相互作用的有限策略的阻碍。在这里，我们试图通过描述一个新的过程来填补知识空白，在这个过程中，生物膜内的细胞交换它们的外膜（OM）脂蛋白，导致表型变化。我们的模式生物，黄粘球菌，是一种社会性革兰氏阴性细菌，可以经历多细胞发育，被用来探测生物膜细胞动力学。在初步结果中，我们现在表明OMs也被交换，我们确定了转移所需的细胞蛋白质。我们还表明，转移，这只发生在结构生物膜，涉及亲缘识别，使细胞区分自己与其他密切相关的黄原分枝杆菌分离物。由于转移涉及成本高昂的OM材料的大量移动，我们认为这种交换过程是细胞交流和共享资源的一种合作行为形式。最后，我们发现迁移可以调节群体扩张，并且可能由纳米管结构介导。我们的研究结果具有广泛的意义，因为真核细胞被广泛认为可以交换细胞成分，而在细菌系统中，蛋白质交换开始被认为是一个普遍的过程，涉及通信和各种细胞过程。我们的遗传系统已经准备好解决这些基本问题。在这里，在目标1中，我们将使用遗传方法来识别参与转移的蛋白质的细胞补体，并定义它们的相互作用以及纳米管在转移中可能发挥的作用。目的2将描述亲属识别在转移中的机制，并定义细胞-细胞识别的遗传决定因素。目的3将确定OM交换如何调节游动扩张及其在发育和包膜稳态中可能发挥的作用。这些共同的努力将促进我们对生物膜细胞如何相互作用、相互识别和交换细胞物质的机制理解，从而导致不同于浮游细胞或分离细胞的表型变化。

DESCRIPTION (provided by applicant): Biofilms are surface attached microbial communities that predominates infection sites, and are of keen medical importance as they resist killing by antibiotics and the immune system. Progress in understanding how biofilm cells interact to elicit phenotypic changes has been impeded by limited strategies to probe their cellular interactions. Here, we seek to fill-in knowledge gaps by describing a novel process where cells within biofilms exchange their outer membrane (OM) lipoproteins, which result in phenotypic changes. Our model organism, Myxococcus xanthus, is a social gram-negative bacterium that can undergo multicellular development, is used to probe biofilm cellular dynamics. In preliminary results we now show that OMs are also exchanged and we identify cellular proteins required for transfer. We also show that transfer, which only occurs in structured biofilms, involves kin recognition whereby cells distinguish themselves from other closely related M. xanthus isolates. As transfer involves costly bulk movement of OM material, we believe this exchange process is a form of cooperative behavior where cells communicate and share resources. Lastly, we show transfer regulates swarm expansion and may be mediated by nanotube structures. Our results have broad implications as eukaryotic cells are widely known to exchange cellular components, and in bacterial systems, protein exchange is beginning to be appreciated as a prevalent process involved in communication and diverse cellular processes. Our genetic system is well poised to tackle these fundamental issues. Here, in Aim 1 we will use genetic approaches to identify the cellular complement of proteins involved in transfer, and define their interactions an the role nanotubes might play in transfer. Aim 2 will characterize the mechanism of kin recognition in transfer and define the genetic determinant for cell-cell recognition. Aim 3 will determine how OM exchange regulates swam expansion and a role it might play in development and envelope homeostasis. These combined efforts will advance our mechanistic understanding of how biofilm cells interact, recognize one another and exchange cellular material, which results in phenotypic changes that are distinct from planktonic or isolated cells. PUBLIC HEALTH RELEVANCE: Biofilms are dense microbial mats that are medically important as they account for most microbial infections. Biofilm infections are difficult and expensive to treat because they are resistant to the host immune system and antimicrobial agents. This proposal seeks to investigate novel cell interactions in biofilms, which may advance our understanding of biofilms and consequently lead to improved intervention strategies.